JP2009-204086A discloses a load sensing valve device that maintains a flow dividing ratio according to the opening of each main valve, regardless of load pressure variation in a plurality of actuators. Moreover, as a technology related to this type, there is, for example, a load sensing valve device 200 disclosed in FIG. 2.
The load sensing valve device 200 shown in FIG. 2 includes a valve body B that incorporates a main valve V1 and a compensator valve V2. A pump port 1 connected to a variable displacement pump (not illustrated), a bifurcated connection passage 2 leading from the pump port 1, and actuator ports 3 and 4 connected to the actuators, are formed in the valve body B.
A main spool MS of the main valve V1 is provided in the valve body B in a slidable manner. A first annular groove 9 is formed at the middle of the main spool MS, and a second annular groove 10 and a third annular groove 11 are formed on either side of the first annular groove 9.
Moreover, a spool hole for the main spool MS has a first annular recessed portion 12 formed at the center of the connection passage 2, and a second annular recessed portion 13 and a third annular recessed portion 14 formed at positions on respective outer sides of the connection passage 2.
The main spool MS is usually kept in a neutral position as shown in FIG. 2 by an effect of a spring force of a centering spring 15.
When the main spool MS is in the neutral position, the first annular groove 9 directly faces the first annular recessed portion 12, and the second annular groove 10 and the third annular groove 11 directly face the actuator ports 3 and 4, respectively.
When a pilot pressure is guided to one of either the first pilot chamber 16 or the second pilot chamber 17 from a state in which the main spool MS is kept in the neutral position, the main spool MS moves in either of the right or left direction in FIG. 2 and is switched.
The compensator valve V2 is constructed to have a compensator spool CS serve as a main element thereof, the compensator spool CS being incorporated into the valve body B in a slidable manner. The compensator spool CS has an annular first groove 18, second groove 19, and third groove 20 formed thereon. Moreover, one end of the compensator spool CS faces the pressure chamber 21, and the other end thereof faces a maximum load pressure introduction chamber 22.
A passage 23 is formed in the compensator spool CS, which communicates with the pressure chamber 21. An opening portion 23a of the passage 23 communicates with a relay port 24 formed in the valve body B. The opening portion 23a is opened constantly to the relay port 24 regardless of a moved position of the compensator spool CS. Moreover, a damper orifice 23b is formed between the opening portion 23a and the passage 23.
Moreover, the relay port 24 communicates constantly with the first annular recessed portion 12 of the main valve V1. When the main spool MS switches from the neutral position shown in FIG. 2 to either a left or a right position, pressured fluid flows from the pump port 1 into the relay port 24, and the pressure of the relay port 24 is guided to the pressure chamber 21 via the passage 23.
The compensator spool CS is kept at a position in which pressure guided from the relay port 24 to the pressure chamber 21 is balanced with a maximum load pressure guided towards the maximum load pressure introduction chamber 22. Furthermore, the opening of the flow passage flowing from the relay port 24 to the first groove 18, that is, the opening of the compensator throttle portion a, becomes the smallest when the compensator spool CS is at the position shown in FIG. 2, and increases as the compensator spool CS moves in the right direction.
Moreover, a U-shaped flow passage 25 is formed in the valve body B, and one end of the flow passage 25 constantly communicates with the first groove 18 of the compensator spool CS.
Therefore, the pressured fluid flowing into the relay port 24 flows into the flow passage 25 via the compensator throttle portion a. The pressured fluid flowing into the flow passage 25 pushes open either the load check valve 26 or 27. Furthermore, the pressured fluid is guided to either the second annular recessed portion 13 or the third annular recessed portion 14, via either the second groove 19 or the third groove 20.
Moreover, the other end of the flow passage 25 communicates with the first pressure introduction port 28a and the second pressure introduction port 28b, according to the moved position of the compensation spool CS. The first pressure introduction port 28a opens towards the flow passage 25 when the compensator spool CS is in the position as shown in FIG. 2. The compensator spool CS then closes during a course of moving in the right direction in FIG. 2.
The second pressure introduction port 28b is in a substantially fully closed state when the compensator spool CS is in the position as shown in FIG. 2, and when the compensator spool CS moves in the right direction in FIG. 2, the second pressure introduction port 28b communicates with the flow passage 25.
However, an orifice is formed in the second pressure introduction port 28b as shown in FIG. 2, to reduce the opening of the second pressure introduction port 28b than the opening of the first pressure introduction port 28a. 
The first pressure introduction port 28a and the second pressure introduction port 28b communicate with a pressure introduction chamber 29 formed in the compensator spool CS.
The pressure introduction chamber 29 faces one end of a selector valve 30. The other end of the selector valve 30 faces a pressure relay chamber 31 that communicates with the maximum load pressure introduction chamber 22.
Therefore, a pressure of the pressure introduction chamber 29, that is to say, a load pressure of an actuator connected to the main valve V1, and a maximum load pressure guided to the maximum load pressure introduction chamber 22, act on the selector valve 30.
When the load pressure of the actuator exceeds the pressure of the maximum load pressure introduction chamber 22 at this time, in other words, when the load pressure of the actuator becomes higher than the load pressure of the other actuators, the selector valve 30 opens by the effect of the load pressure of the actuator, and the load pressure of the actuator is guided to the maximum load pressure introduction chamber 22.
When the load pressure of the actuator is lower than the pressure of the maximum load pressure introduction chamber 22, the selector valve 30 is kept in a closed valve state by the effect of the pressure of the maximum load pressure introduction chamber 22.
As such, a maximum load pressure is selected among the load pressures of the actuators connected to the plurality of main valves, and is introduced to the maximum load pressure introduction chamber 22 of each of the main valves and is guided to a tilt angle control section (not illustrated).